Underground water and sewer lines, e.g., feed lines for residential water and sewer users or irrigation projects such as for golf courses, often employ fittings such as tees, wyes and T-wyes at spaced intervals in the main pipeline and lateral pipes as joints between those pipes. Conventionally, the main and lateral pipes, as well as the fittings, are formed of a plastic material such as polyvinyl chloride and the pipe joints are gasketed to seal the two pipes to the fitting at the joint.
Fabricated fittings for joining opposite ends of sewer pipes such that a lateral pipe can be coupled to the fitting are generally very short in length, i.e., on the order of 2 to 3 feet, and typically have at least one lateral opening formed with a bell. Fittings are conventionally manufactured at a manufacturing site by applying a plug inside the fitting, heating the wall of the fitting where the lateral opening is to be formed and drawing the plug through a pilot opening in the wall to enlarge the opening to form a lateral opening with a flange. Heat is typically applied to the plastic fitting at the manufacturing site by applying a canvas coated with silicone on both the inner and outer sides of the fitting about the pilot hole. Electrical current is applied and the PVC material is heated to approximately 275.degree. F., which softens the material. With the plug inside the fitting and the material softened, the plug is typically pulled downwardly from within the fitting to form the lateral opening or socket. Conventionally, a hydraulic cylinder is used to pull the plug through the pilot hole to enlarge the opening. Once the lateral opening is formed, a short belled section of pipe may be solvent-welded to the flange about the opening to complete the fitting.
At a job site, for example, in a residential tract, water or sewer lines formed of PVC are typically laid alongside a number of residential lots, necessitating numerous lateral connections to provide water and sewer service to the residences. The contractor does not have the capability to form in the field lateral openings along the length of a long pipeline section. Hence, the contractor typically uses the fitting. The PVC pipe is normally provided in large lengths, i.e., on the order of 13 to 20 feet. The joints between these long pipe sections usually do not physically line up with the desired location for the lateral pipes. To construct the joint, the contractor will typically cut the long pipe intermediate its ends, bevel both ends, insert the beveled end into an end of a fitting and insert the end of the next long section into the opposite end of the fitting. The lateral pipe will then be inserted into the bell on the side of the fitting. However, fittings are relatively expensive and costly and laborious to install. As set forth herein, the present invention provides apparatus and methods for forming a lateral opening in a main plastic pipeline at any location along the length of the pipeline and at the job site, thereby eliminating the need for costly fittings.
Further, it will be appreciated that main pipelines and lateral pipes in pressurized fluid systems have a tendency to separate from one another at the joint. For example, water pressure tends to cause a separation of the main and lateral pipes. Customary practice to prevent such separation is to provide a concrete block behind the fitting which, in turn, bears against undisturbed soil so that the water pressure will not separate the lateral pipe from the fitting. Where pipes and fittings formed of metal materials are used, one practice has been to apply a pair of metal collars to the lateral pipe and to the bell of the fitting, with bolts between the collars such that the lateral pipe and fitting cannot be separated under water pressure. This, in effect, makes rigid the joint between the lateral pipe and the fitting and does not afford any Form of stress relief at the joint. Another type of metal restraint at the joint between a lateral pipe and a main pipe comprises three semi-cylindrical metal sections. See, for example, Russian Patent No. SU 1620-765-A. As illustrated there, two semi-circular sections are clamped about the lateral pipe, which also has projections which extend partially about the main pipe at the joint. The projections and portions of the two cylindrical sections about the lateral pipe are secured to a third semi-cylindrical section about the main pipe on a side thereof remote from the lateral pipe to provide a rigid joint. This type of restraint, however, does not afford stress relief at the joint and, in any event, is formed of a multiplicity of parts and parts formed of metal which do not afford resistance to corrosion.